The major purposes of this project are to improve our means for diagnosis, understanding of pathogenesis, and evaluation of prognosis of a variety of renal glomerulonephropathies. These objectives will be achieved by analysis of renal biopsies with the use of correlated light, immunofluorescence and electron microscopy. New cases, and in particular, followup biopsies will be performed in patients with or without therapy in order to evaluate the natural or therapeutically modified history of proliferative and membranous glomerular diseases. In addition, we wish to enrich knowledge with respect to the morphologic variations which may occur within a specific diagnostic category of renal glomerular diseases and to determine what significant relationship such variations may have on ultimate progress or resolution of the disease. Lymphocellular immune reactivity with selected renal or streptococcal antigens and immunohistochemical staining of tissues are methods that will be utilized to assess possible pathogenetic significance of hypersensitivity reactions in glomerulonephropathies. Included in this study is a comparative evaluation of host renal disease and the variety of light, immunofluorescence, and ultrastructural alterations occurring in renal allografts in patients receiving kidney transplants. The aim in this aspect of the study is to determine the nature and proportional contribution to graft disease of rejection reactions, recurrence in the graft of original host or new primary renal disease, and mechanical factors of surgery and infection.